From the top to the bottom.

Having climbed the Eiffel Tower one day, we went on a tour of the sewers the next.

Yes, there were rats (in the distance) and no, the smell was not bad. Not good, but not bad.

The above is a very small tunnel. The biggest is about 5m (15 foot) in diameter.

A la Indianna Jones, one of the ways they clean the sewers is to send an enormous ball down the tunnels. As it floats on the liquid and also touches the roof of the tunnel it creates a high speed flushing effect between it and the bottom of the tunnel as it moves and thus sweeps the heavy stuff ahead of it. Tricky, non?
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